Modification of the Fritsch-Buttenberg-Wiechell rearrangement: a facile route to unsymmetrical butadiynes

A modification of the Fritsch-Buttenberg-Wiechell rearrangement has been used to form unsymmetrically substituted 1,3-butadiynes from 1,1-dibromo-olefin precursors. The reaction proceeds via lithium-halogen exchange, followed by migration of the aryl or alkynyl moiety to provide the butadiyne framework. The facile formation of the dibromo-olefins in three steps from commercially available aryl aldehydes or carboxylic acid chlorides makes this procedure an attractive alternative to traditional methods for butadiyne synthesis. (C) 2001 Elsevier Science Ltd. All rights reserved.